Simple known ladders generally do not need to be foldable, since their successive step rods are already nested within the plane of the ladder main frame and, thus, are most compact.
Recent ladders tend to feature wider steps for increased comfort and safety of the users. These steps protrude from the plane of the main ladder frame and, thus, require a larger storage area for the ladder.
Folding mechanisms have been proposed in the art for pivoting the step panels of these latter ladders in between operative and inoperative (unobstrusive) conditions. Typical of these mechanisms is the parallelogram linkage assembly disclosed in Canadian Pat. No. 1,004,195, issued Jan. 25, 1977 to John A. Herwynen. The main disadvantage of this patent is that linkage elements still project outwardly the plane of the ladder main frame when in folded condition.
No solution has been found as yet to bring the linkage assembly within the plane of the main ladder frame when the latter is completely folded.